US8847499B2 - Photocell controlled LED driver circuit - Google Patents

Photocell controlled LED driver circuit Download PDF

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Publication number
US8847499B2
US8847499B2 US13/524,246 US201213524246A US8847499B2 US 8847499 B2 US8847499 B2 US 8847499B2 US 201213524246 A US201213524246 A US 201213524246A US 8847499 B2 US8847499 B2 US 8847499B2
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node
light sensing
output
coupled
led driver
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US20120319591A1 (en
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Mingliang Wu
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RAB Lighting Inc
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RAB Lighting Inc
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    • H05B37/0218—
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B47/00—Circuit arrangements for operating light sources in general, i.e. where the type of light source is not relevant
    • H05B47/10—Controlling the light source
    • H05B47/105—Controlling the light source in response to determined parameters
    • H05B47/11—Controlling the light source in response to determined parameters by determining the brightness or colour temperature of ambient light
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection
    • Y02B20/46—

Definitions

  • the present invention relates to LED driver circuits, and particularly, to an LED driver circuit incorporating automatic on and off control based on ambient light sensing.
  • One prior art design for a light driver includes driver integrated circuits providing the required light supply signals and a microcontroller to provide control logic and other functionality required for driving the lights.
  • An I/O port of the microcontroller is coupled to a luminous detection circuit, including a cadmium sensor, a photo diode, or a phototransistor, and provides on and off control of the light depending on the ambient light detected by the luminance detection circuit.
  • PFC controller for example, a current-mode PFC controller operating in transition mode, and a flyback converter providing an isolated, low cost, low component count voltage to LEDs.
  • PFC controllers packaged as an integrated circuit can include a monitor/disable input used to detect and provide protection, for example, from overvoltage of the PFC pre-regulator and/or feedback failure.
  • An exemplary monitor/disable input operates as an output voltage monitor and disables the controller if the voltage drops below a particular threshold, thus providing the potential for on and off control via a voltage control signal.
  • the present invention may comprise one or more of the features recited in the attached claims, and/or one or more of the following features and combinations thereof.
  • An illustrative LED driver circuit includes an automatic on and off control function using a light sensing circuit having a light sensing element reacting to ambient light.
  • the circuit uses flyback converter topology and a power factor correction (PFC) controller.
  • the light sensing function is provided by coupling the output of the light sensing circuit to a PFC controller monitoring/disable input, thus providing easily implemented on and off control of the LED controller, and thus the LED driver circuit output.
  • a light sensing element such as a photocell having a resistance that varies with ambient light (e.g., a photoresistor or light dependent resistor (LDR)) can be used in a voltage divider to provide a voltage output signal that varies with ambient light.
  • LED(s) commonly refers to light emitting diodes, however, herein LED more broadly refers to light emitting semiconductor devices, including for example, but not limited to, light emitting diodes and laser diodes.
  • One illustrative LED driver circuit with automatic on and off ambient light control includes a power factor correction controller, the controller including a disable input that enables/disables an output of the LED driver circuit; and a light sensing circuit including a light sensing element, an output of the light sensing circuit changing based on the light sensing element responding to changes in ambient light, the output of the light sensing circuit coupled to the disable input of the controller; wherein the output of LED driver circuit is enabled/disable in response to the ambient lighting.
  • the light sensing element can be, for example, a photocell.
  • the illustrative LED driver circuit can further include a flyback converter, the output of the LED driver circuit provided by the flyback converter.
  • the light sensing circuit further includes a first resistor and a first capacitor in parallel and defining a first and second node, the light sensing element coupled to the first node and an opposite terminal defining a third node, the second node coupled to a ground, the third node coupled to a voltage supply, and the first node defining the output of the light sensing circuit.
  • the light sensing circuit further includes a first and second resistor, a first capacitor, and a first transistor, the first resistor and first capacitor in parallel and defining a first and second node, the light sensing element coupled to the first node and an opposite terminal defining a third node, the transistor having a base, emitter, and collector, the base coupled to the first node, the emitter coupled to the second node, the collector forming a fourth node, the second resistor coupled between the fourth node and the third node, the second node coupled to a ground, the third node coupled to a voltage supply, and the fourth node defining the output of the light sensing circuit.
  • the light sensing circuit further includes a first, second, and third fourth resistor, a first capacitor, and a first operational amplifier, the first resistor and first capacitor in parallel and defining a first and second node, the light sensing element coupled to the first node and an opposite terminal defining a third node, the operational amplifier having an output, an inverting input, and a non-inverting input, the inverting input coupled to the first node, the non-inverting input defining a fourth node, the second resistor coupled between the fourth node and the third node, the third resistor coupled between the fourth node and the second node, the second node coupled to a ground, the third node coupled to a voltage supply, and the output of the operational amplifier defining the output of the light sensing circuit.
  • the light sensing circuit further includes a first, second, third, and fourth resistor, a first capacitor, and a first operational amplifier, the first resistor and first capacitor in parallel and defining a first and second node, the light sensing element and the fourth resistor in parallel and coupled to the first node and an opposite terminal defining a third node, the operational amplifier having an output, an inverting input, and a non-inverting input, the inverting input coupled to the first node, the non-inverting input defining a fourth node, the second resistor coupled between the fourth node and the third node, the third resistor coupled between the fourth node and the second node, the second node coupled to a ground, the third node coupled to a voltage supply, and the output of the operational amplifier defining the output of the light sensing circuit.
  • FIG. 1 is a schematic diagram of an illustrative LED driver circuit according to the present invention
  • FIG. 2 is a schematic diagram of a first illustrative light sensing circuit for use with the LED driver circuit of FIG. 1 ;
  • FIG. 3 is a schematic diagram of a second illustrative light sensing circuit for use with the LED driver circuit of FIG. 1 ;
  • FIG. 4 is a schematic diagram of a third illustrative light sensing circuit for use with the LED driver circuit of FIG. 1 ;
  • FIG. 5 is a schematic diagram of a fourth illustrative light sensing circuit for use with the LED driver circuit of FIG. 1 .
  • An illustrative LED driver circuit 20 includes an automatic on and off control function using a light sensing circuit 30 a , 30 b , 30 c , or 30 d having a light sensing element PC reacting to ambient light.
  • the circuit uses a flyback converter 23 and a power factor correction (PFC) controller U 1 .
  • the light sensing function is provided by coupling the output 38 of the light sensing circuit 30 a - 30 d to a PFC controller monitoring/disable input 21 , thus providing easily implemented on and off control of the controller U 1 , and thus the LED driver circuit output 26 and 28 .
  • a light sensing element PC such as a photocell having a resistance that varies with ambient light (e.g., a photoresistor or light dependent resistor (LDR)) can be used in a voltage divider to provide a voltage output signal 38 that varies with ambient light.
  • a photoresistor or light dependent resistor (LDR) can be used in a voltage divider to provide a voltage output signal 38 that varies with ambient light.
  • LDR light dependent resistor
  • Other photo sensing elements known in the art can also be used, for example, photo sensing elements that respond to ambient light with changes in resistance, voltage, or current, for example, photo transistors.
  • a power line LED driver circuit 20 is shown on FIG. 1 and uses typical flyback converter topology 23 and a power factor correction (PFC) circuit, implemented in the illustrative embodiment with a PFC controller, for example IC L6564 available from STMicroelectronics of Coppell, Tex.
  • the LED driver circuit shown in FIG. 1 is universal in that the power input across nodes 22 and 24 can be a 120V to 277V AC line input or a DC supply input.
  • Optocoupler U 2 provides an LED output feedback signal, and can be voltage or current feedback provided to the PFC controller U 1 .
  • Power supply U 3 is a 15V dc supply for PFC controller U 1 .
  • PFC controller U 1 in the illustrative embodiment, L6564 is a ten pin IC device having pin functions common to such controllers, including devices L6561 and L6562: Pin 1 (INV), pin 2 (COMP), pin 3 (MULT), pin 4 (CS), pin 7 (ZCD), pin 8 (GND), pin 9 (GD), pin 10 (Vcc).
  • PFC controller U 1 pin 5 (VFF) can be used for brownout (AC main under voltage) protection.
  • PFC controller U 1 pin 6 (PFC_OK), labeled with reference numeral 21 can be used for output voltage monitoring.
  • PFC controller U 1 pin 6 has two control levels: at about the 2.4V level and at about the 0.25V level. For example, the output of the PFC controller U 1 is disabled when the voltage level at pin 6 exceeds 2.5V or falls below 0.23V. Thus, either control level could be used for on and off control of the output supply 26 and 28 of LED driver circuit 20 .
  • the 0.25V level is selected for on and off control from a light sensing circuit 30 a , 30 b , 30 c , or 30 d , and the output of the light sensing circuit 32 is thus coupled through resistor R 9 at node 21 with U 1 pin 6.
  • the output of PFC controller U 1 is disabled.
  • the voltage at node 21 U 1 pin 6
  • the illustrative light sensing circuit 30 a can be designed to have a low voltage signal (off control) below 0.20V and high voltage control signal (on control) below 2.0V and above 0.30V.
  • LDR light dependent resistor
  • Rp can be less than 1 k ohm. In contrast, at night time, when little to no light is directly onto the photocell, Rp can be higher than 1M ohm.
  • the changes of resistor value due to the light intensity changing can be used as the basis of the on and off control signal at node 38 for the LED driver circuit 20 .
  • FIG. 2 illustrates a first illustrative light sensing circuit 30 a for use with the LED driver circuit 20 of FIG. 1 .
  • light sensing circuit 30 a is a simple circuit using few and inexpensive components for providing a controls signal based on the ambient light sensed by the photocell PC to the LED driver circuit 20 , using the configuration of a simple voltage divider, with the photocell PC coupled between a reference/supply voltage Vcc at node 36 and the V(control) signal at node 32 , and a capacitor C 11 and fixed resistor R 21 in parallel between V(control) signal at node 32 and the reference ground 34 .
  • Vcc reference voltage
  • resistor R 21 resistor R 21 +100 k ohm
  • V (control) 38 can be above 4.5V at day time and less than 0.5V at night.
  • resistor R 21 can be 470 ohm. This configuration provides a positive control logic, i.e., V(control) 38 higher at day time with bright ambient light conditions, and V(control) 38 lower at night time with dark ambient light conditions.
  • FIG. 3 illustrates a second illustrative light sensing circuit 30 b for use with the LED driver circuit 20 of FIG. 1 .
  • the light sensing circuit 30 b of FIG. 3 can provide a reverse control logic voltage level, i.e. V(control) 38 lower in bright ambient light conditions and V(control) higher in dark ambient light conditions.
  • Photocell PC is coupled between the reference/supply voltage Vcc at node 36 and the base of transistor Q 2 at node 32
  • a capacitor C 11 and fixed resistor R 21 are coupled in parallel between the base of transistor Q 2 at node 32 and the reference ground 34
  • the emitter of transistor Q 2 is coupled to the reference ground
  • resistor R 22 is coupled between the supply voltage Vcc at node 36 and the collector of transistor Q 2 .
  • This configuration for light sensing circuit 30 b is able to provide a signal control level from the collector node 38 of transistor Q 2 at PFC controller pin 6 (node 21 ) of about 2.5V; however, because transistor Q 2 has a saturation voltage, the light sensing circuit 30 b of FIG. 2 may not be preferred in the case of electing a low voltage control signal at PFC controller pin 6 (node 21 ), i.e., signal control level that is about 0.25V or below.
  • FIG. 4 illustrates a third illustrative light sensing circuit 30 c for use with the LED driver circuit 20 of FIG. 1 .
  • An operational amplifier U 4 is used in the circuit 30 c of FIG. 4 .
  • This circuit can provide a signal control level voltage of either 2.5 V or 0.25 V available for PFC controller U 1 at pin 6 (node 21 ), with positive or reverse control logic.
  • Resistors R 22 and R 23 provide a voltage divider circuit and output comparison voltage.
  • photocell PC is coupled between the reference/supply voltage Vcc at node 36 and the inverting input of op amp U 4 at node 32 , and a capacitor C 11 and fixed resistor R 21 are coupled in parallel between the base of transistor Q 2 at node 32 and the reference ground 34 , the emitter of transistor Q 2 is coupled to the reference ground and resistor R 22 is coupled between the supply voltage Vcc at node 36 and the collector of transistor Q 2 .
  • FIG. 5 a third illustrative light sensing circuit 30 d for use with the LED driver circuit 20 of FIG. 1 is illustrated.
  • the light sensing circuit 30 d is similar to that shown in FIG. 4 and discussed above except that resistor R 24 with 1M ohm value is added across nodes 32 and 36 , thus in parallel with photocell PC.
  • the LED driver circuit 20 functions normally without photocell PC because resistor R 24 replaces the photocell position.
  • resistor R 24 will not affect the control function as compared to light sensing circuit 30 c.
  • the light sensing circuit 30 a - 30 d only draws a very small current from LED driver circuit 20 .
  • the power supply (not shown) to provide the control circuit Vcc at node 36 can be a single rectifier diode plus a filter capacitor, or drawn from another DC supply, for example, from power supply U 3 .
  • a typical voltage for Vcc can be 3.3V to 15V.
  • the on and off control signal V(control) 38 provided to PFC controller U 1 at pin 6 (node 21 ), can be based on not only the light sensing circuit 30 a - 30 d , but additionally or alternative can be a function of microprocessor or wireless control determined based on any condition, control signal, or ambient light change, with the PFC controller U 1 disable function at pin 6 used to provide the on and off control of the LED driver supplies 26 and 28 .

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US13/524,246 2011-06-17 2012-06-15 Photocell controlled LED driver circuit Expired - Fee Related US8847499B2 (en)

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US13/524,246 US8847499B2 (en) 2011-06-17 2012-06-15 Photocell controlled LED driver circuit

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US201161498238P 2011-06-17 2011-06-17
US13/524,246 US8847499B2 (en) 2011-06-17 2012-06-15 Photocell controlled LED driver circuit

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US (1) US8847499B2 (fr)
CN (1) CN202750279U (fr)
CA (1) CA2780788C (fr)
MX (1) MX2012006986A (fr)
TW (1) TWI478628B (fr)

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JP6073705B2 (ja) * 2013-02-26 2017-02-01 エスアイアイ・セミコンダクタ株式会社 ヒューズ回路及び半導体集積回路装置
CN103715880B (zh) * 2014-01-07 2017-03-01 巨尔(上海)光电照明有限公司 功率因数校正控制电路及电源适配器
CN105848338B (zh) * 2016-04-06 2017-10-31 上海联矽智能科技有限公司 一种普通光敏传感器的高精度实现方法
CN106658191A (zh) * 2016-11-17 2017-05-10 韦笃排 通过usb接口实现电视机与机顶盒同步控制的装置及方法
CN108045299B (zh) * 2017-12-25 2024-03-26 中国重汽集团济南动力有限公司 一种带保护功能的汽车灯光自动控制装置
CN108449845B (zh) * 2018-05-10 2023-09-22 嘉兴星程电子有限公司 一种具有自动光感功能的led灯驱动装置

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Publication number Publication date
TW201301955A (zh) 2013-01-01
TWI478628B (zh) 2015-03-21
US20120319591A1 (en) 2012-12-20
MX2012006986A (es) 2012-12-17
CA2780788C (fr) 2015-03-17
CA2780788A1 (fr) 2012-12-17
CN202750279U (zh) 2013-02-20

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